1. Intense distrust of the catholic church, because the catholic church encourages and accepts racial miscegenation and migrant invaders. In case it is not blindingly obvious: every megachurch pastor can authoritatively call themselves American, and give out religion to other Americans who are by definition better than non-americans who are non-people. It is straight xenophobia and hatred of outsiders driving these organizations. Hence the common association they have with bigotry and nativism.
2. Unregulated church market because of the 1st Amendment. It is legal to create any cult you want and fuck over your worshipers so long as they honestly believe in you and you hold regular, sanctioned worship events.
3. TV. Modern evangelism is a for-profit media network enabled by television broadcasting. It has allowed the SBC, via TBN, to become a truly unified national political agency. This power was then used to corrupt the Republican Party, which in turn has corrupted the SBC into being an annex of the Republican Party. Because the Republicans were corrupted by (lara) Trump, SBC is now corrupted by Trump and will do anything he wants. This was extensively covered in a big scandal a few years ago that saw several prominent ministers resign over their criticism of SBC's ethics, particularly within relation to their child sex abuse scandal.
At the base of it, this is what Americans are like especially in the deep south where they either go in with these people or they submit to roman authority and let millions of mexicans in to displace them and their culture.